Underground conduit.



No. 640,826. Pate nted .Jan. 9, I900.

C. H. SEWALL.

UNDERGROUND CONDUIT.

(Application filgd July 5, 1895.)

2 SheetsSheet I.

(No Model.)

TH:- nomu's PETERS 20., PnuToumov, WASHINGTON 04 c,

(No Model.)

T'atented Ian. '9, I900. D. H. SEWALL.

UNDERGROUND CONDUIT.

(Application filed July 5, 1895.)

I 2 Sheets-Sheet 2.

v fly 4 THE NORRIS PETERS c0 momm'flo" WASHINHTON, a c.

fNrrED STATES FFICY;

PATENT CHARLES H. SEWALL, OF CHICAGO, ILLINOIS.

SPECIFICATION forming part of Letters Patent No. 640,820, dated January 9, 1900.

Application filed m 5, 1395. Serial No. 565,064. (No model.)

To all whom it may concern:

Be it known that I, CHARLES H. SEWALL, a citizen of the United States, residing at Ohicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in the Laying of Underground Conduits for Electrical Conductors; and I do hereby declare that the following is a full, clear, and exact description of the invention, reference being had to the accompanying drawings.

Heretofore conduits have been made either by laying directly in a trench pipes of wood, iron, or clay and tamping around them the previously-removed soil or by embedding the pipes in some plastic material, such as asphalt or a concrete of cement and sand. Another process is to place around mandrels or cores concrete or similar material while in its plastic state, and when such material is sufficiently set to withdraw the cores, leaving receptacles for the introduction of conduc tors; but all these structures have lacked sufficient resistance to tensile strain. The concrete and pipes not being bonded in one mass do not act together under strain, and the conduit is especially weak where said pipes are joined. Such a structure is ill-prepared to withstand settlings and other changes in the soil, and especially in cities it is continually in danger from excavations made under it. The strongest form so far consists of wroughtiron pipes laid in concrete; but these pipes form no bond withthe surrounding material and under strain slip through it. Then the unsupported concrete cracks and throws the ducts out of line, thus breaking or injuring the conductors. In time the pipes, which are completely exposed on their inner surfaces, rust away, leaving rough inner surfaces and undesirable rubbish.

At this writing vitrified tile embedded in cement concrete is much used. It has a smooth interior surface, is durable and cheap, and experience has shown that the comparatively greater strength of iron pipe in newlylaid concrete does not counterbalance the disadvantages of increased cost and early deoay which results with iron pipes.

Conduits in which the ducts are made over cores by tamping concrete around said cores have not proved successful in practice, for

the reason that until strengthened by age they easily deflect and because it is difficult to draw the cores without injury to interior duct-surfaces. v

For those concrete conduits which are formed and set in a factory and carried to lic frames are put wholly or partly around the ducts and socontrived that while the frames will allow plastic mixtures to pass through them they strengthen the structure and by lessening the pressure on the mandrels greatly facilitate their smooth withdrawal. By the use of said mandrels and by the lapping of one frame over the other at joints tubes or ducts of continuously-smooth bore are made. The supporting-frames may be of sheet metal perforated, slotted, or expanded and formed. into suitable shape, or of wirecloth, or of perforated pipes of wrought, cast, or sheet metal, or of pipes of wire-cloth. I prefer the wire-cloth in sheet or pipe form.

In the drawings, Figure 1 is an end view of a conduit-duct, showing the firs-t stage of a process with two rectangular formers and the chamber-forming mandrel in their places; Fig. 2, the same duct as in Fig. 1, but in second stage of process and rectangular cores withdrawn; Fig. 3, the completed duct, the chamber-mandrel having been removed; Fig. 4, a longitudinal section of conduit through dotted line m n of Fig. 2, showing divided chamber-mandrel in relief. Fig. 5 shows in half-plan and half-section a bonding-joint between two blocks of conduit.

Similar letters refer to similar parts throughout the several views.

A represents concrete of cementor sand or a similar material.

B and O are rectangular cores or formers embedded in A during first stage of process.

D and E are respectively the top and bottom pieces of divided chamber-mandrel, and r s the longitudinal line of division.

Gand H are abutting blocks of conduit, and nation with a body of concrete, or similar ma- K recess in blocks G and H.

lie the metal bond for concrete p in recess K.

The process of laying is to first build a suitable foundation of coarse concrete. Upon the top of this foundation is laid a thin layer of fine-grained and richly-mixed concrete. Upon this at the proper distances are placed mandrels D E, Fig. 1, to form ducts, and between said ducts, alternating with the divided mandrels D E, other shapers B and G to form the shells of the ducts. Fine and rich concrete is .then well rammed into the open spaces until shells of proper thickness are made around the chamber-forming cores. (See Fig. 1.) The spacing-cores B and C are then withdrawn and metallic frames F pressed into the concrete forming the duct-shells and fitted into the spaces between them. (See Fig. 2.) The spaces left by the metallic frames between ducts are then filled in with concrete, a foundatiou laid for another tier of ducts, and the divided mandrel removed. (See Fig.

The method of removing from the duct the core or mandrel D E is to first draw the lower.

section E. Preferably the sections D and E are of Wood and are lubricated both on their outer surfaces and on the surfaces along the division-line r s, Fig. 4. The drawing of section E but a slight distance so lessens the diameter of the whole core that the said core is easily moved in either direction Without injuring the interior surface of the duct. The lines shown in Figs. 1 and 2 as separating D and E can be vertical instead of horizontal.

The diagonal line r 3 may be along the top.

and bottom instead of along the sides of the core, the essential point being that the division must extend lengthwise from end to end and be made bias.

The methods so far described contemplate building the structure in an open trench; but it is frequently the case that obstructions are met which necessitate the making of short tunnels. I then make in a factory instead of in the trench concrete conduits containing therequisite number of ducts, and when they are set convey them to the trench and draw them into the tunnel. In the factory-made block and in that of the main structure to which it is to be joined (G and H, Fig. 5) are cut on any or all of the sides or corners corresponding indentations or mortises K. In these niortises I cement strips of slotted or perforated metal or wire-cloth, thus forming the joints, the structure being held by temporary braces until the concrete has sufficiently set. i

What I desire to secure by Letters Patent 1. In an underground conduit, the combiterial, of a layer or door of fine concrete thereon, a shell of concrete formed thereon and forming therewith the duct or conduit-opening, and a filling of concrete, or similar material, inclosing said shell, the Whole being formed into a continuous and integral mass, substantially as described.

2. In an underground conduit, the combination with a body of concrete, or similar material, of a shell of fine concrete formed thereon and forming the duct or conduit-opening, and a filling of concrete, or similar material, inclosing said shell, the Whole being formed into a continuous and integral mass, substantially as described.

3. In an underground conduit, the combination with a body of concrete, or similar ma terial, of a shell of fine concrete formed therc= on and forming theduct or c0nduit-opening, an open binder for reinforcing the upper and side Walls of the conduit-opening, and a filling of concrete or similar material inclosing said shell and binder, the whole being formed into a'continuous and integral mass, substan= tiaily as described.

a. In an underground conduit, the combination with a body of concrete, or similar material, of a layer or floor of fine concrete there= on, a shell of concrete formed thereon and forming therewith the duct or conduit-opening, an open binder for reinforcing the upper and side walls of the conduit-opening, and a filling of concrete, or similar material inclosing said shell and hinder, the whole being formed into a continuous and integral mass, substantially as described.

'5. In an underground conduit, the combination with a foundation or body of concrete, or similar material, of a plurality of shells of line concrete formed thereon side by side and forming the ducts or conduit-openings, and a filler of concrete, or similar material, inclosing said shells and filling the space between and around the same, substantially as described.

6. In an underground conduit, the combination Witha foundation or body of concrete, or similar material, of a plurality of shells of concrete formed thereon side by side and forming the ducts or conduit-openings, an open binder in "the form of a continuous sheet fitting around the upper and side Walls of the several shells, and a filler of concrete, or simi lar material, inclosing and surrounding the binder and the shells, substantially as described.

GHARLES II. SEWALL.

Witnesses Fennnmo A. Deacon, Ronnnr Wrsnnan. 

